Abstract: A scroll fluid apparatus has a revolving scroll and an auxiliary crank as a rotation prevention mechanism. The revolving scroll has a two-layer structure including an auxiliary member having an annular plate portion, and an end plate member having an end plate, the two members being superposed axially. A positioning mechanism is provided between the auxiliary member and the end plate member to position and unite them in a circumferential direction. When the end plate member expands radially due to a rise in temperature, the end plate is displaced radially while being in sliding contact with the annular plate portion. The end plate is fastened to the annular plate portion through a bolt portion at the center thereof, where the amount of radial displacement due to the thermal expansion is the smallest. Accordingly the annular plate portion is not displaced radially and thus, no radial load acts on the auxiliary crank.